- Heat oven to 220℃/fan 200℃. Bring a pot of salted water to the boil. Add the pasta and cook according to package instructions.
- Meanwhile, melt the butter in a large saucepan over medium heat. Add the grated shallot and cook, stirring occasionally, until softened, around 5 minutes. Add the flour and cook for 2 to 3 minutes, stirring frequently.
- Quickly but carefully whisk in the hot milk and increase the heat to medium-high; we’re making a loose béchamel.
- Bring the béchamel to a simmer, whisking often. Reduce the heat down to low and cook until slightly thickened and velvety smooth, 2 to 3 minutes.
- Remove the saucepan from the heat. Whisk in the cheddar, mozzarella and parmigiano reggiano. Add the garlic granules, mustard powder and smoked paprika and whisk together. Taste and season with sea salt and freshly-ground black pepper, to taste.
- Drain the pasta. Add the pasta to the cheese sauce and stir to combine. Pour the mac and cheese into a baking dish and top with the remaining mozzarella. Bake at 220℃/fan 200℃ for 15 to 20 minutes, or until golden brown and bubbling.